1. Field of the Invention
The present invention relates to a moving stage used in a microscope, etc., and movable in one direction (X or Y direction) or two (X and Y directions) directions.
2. Description of the Related Art
The moving stage for microscope, etc., employs a rack/pinion mechanism as its common drive mechanism. In this case, the accuracy with which the rack and pinion are manufactured and assembled together adversely affects the accuracy with which a moving base is driven.
If, for example, there occur warping of the rack and eccentric state of the pinion, or if the extent of paralleling is not adequate in the direction in which a moving base is moved, then the engagement of the pinion with the rack is adversely affects, causing tightening or loosening of these two members and hence an irregular movement of the moving base.
In order to improve these reliability problems, for example, Published Examined Japanese Patent Application 51-44823 proposes a method using a rack of split type and Published Unexamined Utility Model Application H-1-17725 proposes a method using a leaf spring provided between a moving base and a rack.
In the related engineering field, semiconductor wafers, liquid crystal, etc., have become a large-sized in recent years and larger microscopes are also required for inspection. A larger moving stage results in a longer rack. In order to smoothly move the moving base, however, much difficulty has been encountered in manufacturing longer racks accurately or in assembling a rack accurately in a direction parallel to that in which the moving base is moved. Further, the rack/pinion mechanism causes tear and wear at the teeth of the rack and pinion and, if dust or powder resulting from the worn teeth falls on the test specimen, defective products are produced.
In the larger moving stage for the microscope for use in the step of inspecting a semiconductor, it has been proved useful, from the standpoint of manufacture and use, to adopt a frictional drive mechanism, comprised of a toothless straight rail and drive wheel, in place of the conventional rack/pinion mechanism. The rail, if being comprised of a narrowly drawn wire in particular, can be obtained at low cost.
Even in the case of a frictional drive mechanism having the toothless straight rail and drive wheel, if there occurs warping or bending of the rail 1 as shown in FIG. 9A or if an eccentric state occurs at the drive wheel 2, or if an adequate extent of flatness is not achieved at a mount face on which the rail is mounted or if an adequate extent of paralleling is not achieved in a direction in which the moving base is moved (see FIG. 9B), then a partial tightening or loosening occurs at these engaged areas between the rail 1 and the drive wheel 2 as in the case of the aforementioned rack/pinion mechanism so that some inconvenience is involved at the time of operation. In this case it is not possible to, unlike the aforementioned rack, provide a split type groove in a narrow rail, such as a wire. It is necessary that, in order to urge the rail 1 toward the drive wheel 2 with the use of a leaf spring, the rail be supported by a plate seat made up of a rigid body and the plate seat be urged by a leaf spring, etc. In order to maintain the rigidity of the plate seat supporting a very long rail or wire in the larger moving stage, the cross-section of the plate seat has to be made great, thus leading to an increase in size of the plate seat and in manufacturing cost.
There is also a method for urging the drive wheel 2 toward the rail 1 by an elastic member. In this case, accuracy in manufacturing and assembly of these component parts is required, resulting in an increase in cost and an increase in the number of component parts involved. In a structure as shown in FIG. 10, a rail 1 is pressed by an elastic member 4 bonded to the outer periphery of a drive wheel 2 mounted integral with an operation handle 3. Such a structure has a drawback in that, when the operation handle 3 is released from the operator's hand after the rotation of the drive wheel 2 has been stopped, a bounce occurs on the "moving base" side due to the elasticity of the elastic member 4. If, therefore, the moving base is positionally so displaced in the case where it is actually applied to a microscope, the specimen is, together with the moving base, displaced as one unit, resulting in a displacement of an observation image.